select distinct owner schema_name
from dba_segments
where owner in (select username from dba_users where default_tablespace not in ('SYSTEM','SYSAUX'))
and owner in(select table_owner from dba_tab_partitions)
order by owner;
Or
select distinct owner schema_name
from dba_segments
where owner not in ('SYSTEM', 'XDB', 'SYS', 'TSMSYS', 'MDSYS', 'EXFSYS', 'WMSYS', 'ORDSYS', 'OUTLN', 'DBSNMP')
and owner in(select table_owner from dba_tab_partitions)
order by owner;